Dash and wedge symbolism

The dash and wedge symbolism described above is routinely used by chemists to represent three-dimensional structures of molecules. The symbolism is based on the following conventions ... 

In the first diagram, which is how we usually draw the structure, all the atoms lie on the plane of the paper. In the second structure, we use dash and wedge symbols to indicate that one of the bonds points toward us and the other points away. 

Methyl isocyanate, CH3NCO, is used in the manufacture of insecticides, such as carbaryl (Sevin). In the CH3NCO molecule, the three H atoms and the O atom are terminal atoms and the two C and one N atom are central atoms. Draw the structure of this molecule, using dash and wedge symbols, and indicate the various bond angles. 

PRACTICE EXAM PLEA Sketch, by using dash and wedge symbols, the methanol molecule, CH3OH. Indicate the bond angles in this molecule. 

Sketch, by using the dash and wedge symbolism, the H2NCH2CHO molecule, and indicate the various bond angles. 

We can also draw these stereoisomers by using the dashed and solid wedge symbols, together with a line diagram for the oxalate anion. 

For simpler representation on paper, it is more covenient to think of the four bonds, which unite the four different substituents to the carbon atom, as proceeding from the centre of the atom but to the same comers as in 12.5) to 12.7). Then 12.10) becomes an acceptable representation of one of the enantiomers of lactic acid, and 12.11) of the other. The wedges imply that the atoms at their broad edges are above the plane of the paper and those at the end of the lines of the dashes are below [ 12.10) is presented in the same aspect as 12.6) In a crowded molecule, or for speed of handwriting, the wedges may be replaced by thick lines as in 7.11) but the dashes should not be replaced by three dots, the symbol for a hydrogen bond. 

It does not matter whether the CH3 group is placed on the line, wedge, or dash. But don t forget to indicate that the drawing is a transition state by surrounding it with brackets and using the symbol that indicates a transition state (the telephone pole). 

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